螺旋焊缝管道的开裂原因

采用光学显微镜、扫描电子显微镜、能谱仪、维氏硬度仪及金相观察等分析手段,对开裂螺旋焊缝管进行取样分析,利用冲击试验测试了管道母材的抗开裂能力。结果表明：该管道焊缝存在明显缺陷,缺陷类型包括存在于焊缝中的焊缝金属裂纹和夹杂,存在于热影响区中的焊趾裂纹和焊接裂纹,同时在热影响区及母材中存在夹杂。在高外载作用下,由于焊缝区硬度高于热影响区及母材的硬度,使得焊趾裂纹先于焊缝金属裂纹向热影响区扩展。热影响区中沿轧制方向排列的层状夹杂的存在促进了裂纹的扩展,形成层状撕裂,最终导致管道沿热影响区开裂直至母材。

Analysis on cracking causes of spiral welded pipeline

This paper analyses the sampling of cracked spiral weld seam from a pipe with optical microscope, scanning electronic microscope, energy dispersive spectrometer, Vickers hardness tester, and metallographic observation and other analysis means, and tests the anti-cracking performance of base material of pipeline with impact tests. The results show that there are obvious defects in pipeline seam, the types of defects contain welding metal cracking and inclusions in welding seam, weld toe cracks and weld cracks in HAZ, induding inclusion both inHAZ and base material. As the hardness of the welding area is higher than that of the HAZ and base material under higher stress, the weld toe crack spreads to the HAZ earlier than the welded metal cracks. The layered inclusion arranged in rolled direction in the HAZ increases the spread of cracks and thus forms layered cracks, which finally cause pipeline cracking to spread to base material along HAZ.